Polyamide moulding compositions

ABSTRACT

POLYAMIDE MOULDING COMPOSITIONS CONTAINING AS A MOULD REMOVAL AGENT 0.01 TO 10% BY WEIGHT OF AN N-SUBSTITUTED CYCLIC IMIDE.

United States Patent 01 fice 3,557,132 Patented Jan. 19, 1971 ABSTRACTOF THE DISCLOSURE Polyamide moulding compositions containing as a mouldremoval agent 0.01 to 10% by weight of an N-substituted cyclic imide.

4 Claims The present invention relates to polyamides which contain animido compound as additive to facilitate their removal from moulds inwhich they have been shaped in the molten state.

It is already known to add natural or synthetic waxes, fatty alcohols ortheir hydroxyalkylation products, fatty acids or their alkali metal oralkaline earth salts, fatty acid nitriles, fatty acid amides or fattyamines to polyamides as mould parting agents.

These mould parting agents, are usually added to the polyamide itself,being either homogeneously mixed with the granular or pulverulentpolyamide before it is shaped or homogeneously distributed in the moltenpolyamide by means of a suitable mixing device such as stirrers,kneaders, extruders, etc. Addition of the mould parting agents to thepolyamide-forming monomers before polymerisation is not possible in thecase of most mould parting agents, e.g. natural or synthetic waxes,fatty amines, fatty acids, their salts or esters, and fatty acidnitriles, since they either decompose at the temperatures necessary forpolymerisation or react with the carboxyl or amino end groups of thepolyamides and thus lose their activity.

Some of the mould parting agents hitherto described are not sufficientlyeffective, e.g. the fatty alcohols, their hydrooxyalkylation productsand fatty acid amides. Others promote degradation of the polyamides orprolonged heating to temperatures above the melting point, e.g. fattyacids and their salts.

It has now been found that the removal of shaped polyamides from mouldsin which they have been moulded in the molten state is facilitated byadding monomeric N-substituted cyclic imides as mould parting agents tothe polyamides before, during or after their production. It isparticularly preferred that monomeric N-substituted cyclic imides beadded to the polyamide forming monomers before polymerisation.

The invention thus relates to polyamide moulding compositions whichcontain, as mould parting agents, N-substituted cyclic imides inquantities of from 0.01 to 10% by weight, and if desired also the usualpolyamide additives.

The polyamides acording to the present invention are solid polymers inwhich the monomers are linked together via amide bonds, for examplepolycondensates of diamines and dicarboxylic acids, e.g. hexamethylenediamine, decamethylene diamine, ethylene diamine,trirnethyl-hexamethylene diamine, 1,4 bis-aminomethylcyclohexane,

m-xylylene diamine, or 4,4-diaminodicyclohexylmethane 5 with adipicacid, decanedicarboxylic acid, oxalic acid, 1,4- cyclohexanedicarboxylic acid, terephthalic acid or isophthalic acid, orpolycondensates or polymers of aminocarboxylic acids or their lactams,e.g. aminocaproic acid, amino decanoic acid, caprolactam or laurinlactam, or polycondensates or polymers of several of the above mentionedcomponents.

N-substituted cyclic imides in accordance with the present invention arepreferably monomeric compounds of the formula:

wherein R denotes a difunctional aliphatic, cycloaliphatic, aromatic,aliphatic-aromatic or aromatic-aliphatic hydro- 25 carbon radical or theradical and R denotes a monofunctional aliphatic, cycloaliphaticaromatic, aliphatic-aromatic or aromatic-aliphatic hydrocarbon radicalor the radical The radical R may, for example, be an alkyl radical(preferably C to C a cycloalkyl radical (preferably C C which may alsobe further substituted by alkyl (preferably C C an optionally alkyl(preferably C substituted phenyl radical or a phenyl substituted alkyl(preferably C -C radical. The following are examples of such radicals:

R is preferably a difunctional alkyl radical (preferably C -C or abinuclear aromatic hydrocarbon radical. The following are examples of RThe N-substituted cyclicimides used preferably contain at least onealiphatic radical with 12 or more carbon atoms in the chain.

The following are examples of the compounds to be used in the presentinvention 4 (R alkyl, cycloalkyl-, aralkyl or aryl radical.)

Cl3I'I35-CH C O /NR CH2-CO (R=alkyl-, cycloalkyl-, aralkyl- Or arylradical.)

C O CLIC121I2:&

N -(oi1:) EN

CigHzi-CIL- C 0 For these compounds to be most effective, the acidradical should not be aromatic.

The imide-containing mould parting agents are added to the polyamides inquantities of 0.01 to 10 and preferably 0.1 to 2% by weight. Owing tothe excellent ther mal stability and compatibility of the parting agentswith polyamides, they may be added to the polyamide forming startingmaterials, whereupon polymerisation is carried out in known mannerintermittently, egg. in autoclave, or continuously, e.g. in tubereactors, if desired with Water or compounds which liberate water ascatalyst or under anhydrous conditions using alkaline catalysts,preferably in the presence of N-alkyl substituted carboxylic acidamides, e.g. caproic acid stearylamide or palmitic acid dodecylamide aschain stabilisers.

Alternatively, the mould parting agents may be dis tributedhomogeneously, if desired in the form of concentrates in the polyamidesduring or after polymerisation, by means of suitable mixing apparatusessuch as stirrers, kneaders or extruders.

In addition to the mould parting agents, the polyamides may contain theusual additives such as pigments, dyes,

r heat and light stabilisers, optical brightening agents, fillers suchas glass fibres or asbestos fibres, plasticisers, agents which promotecrystallisation and chain breaking agents. Polyamides which contain themould parting agents according to the present invention are eminentlysuitable for the production of articles of complicated shape which aredifficult to remove from moulds, such as combs, housings, cylindricalparts with narrow bores, bearing bushes and gear wheels. One advantageof the polyamides produced according to the invention is that mouldingtemperatures of 120 C. and more can be used without difficulties arisingin removing pointed tips from moulds. Owing to the high mouldingtemperature, the tips are obtained in crystalline for-m in which thetensile strength, compression strength, elastic modulus, hardness andabrasion resistance are greater than in comparable parts that areproduced at lower moulding temperatures for the purpose of avoidingdifficulties in removal from the mould.

EXAMPLE 1 10 kg. portions of caprolactam are polymerised in an autoclavein the usual manner at 270 C. with the addition of 300 g. ofaminocaproic acid as catalyst, 40 g. of caproic acid stearylamide aschain breaking agent, 1 g. of finely ground talcum as crystallisationpromoter and 50 g. (0.5%) of different mould parting agents. Thefinished polyamide melt is then spun in water to form a filament ofabout 3 mm. diameter and chopped up into granules which are freed frommonomeric constituents by boiling with water, and dried.

The products obtained are worked up in a conventional plunger mouldingpress (e.g. of the type EH of Eckert & Ziegler) under the followingconditions:

Moulding temperature (temperature of composition)- Temperature ofnozzle250 C.

Moulding pressure800 kp./cm.

After pressure800 kp./cm.

Temperature of mould- C.

Cycle-25 secs.

Including cooling tirne-7.5 secs.

(For some of the products, the cooling time and hence the cycle must beprolonged.)

The moulding is a circular plate of 80 mm. diameter and 1 mm. wallthickness with 6 radical reinforcement ribs 2 x 2 mm. in cross section.In addition, 6 reinforcement ribs of the same cross-section in the formof circular arcs extend from a distance of mm. from the outer edge ofthe plate. The moulding is started with a central gate and is removedfrom the apparatus with 7 symmetrically arranged ejector pins.

The force required to remove the moulding, which is a measure of theease of removal from the mould, is determined as follows:

A spring arranged centrally in the apparatus presses uniformly againstthe ejection pins. The spring excursion required for ejection isindicated by trailing pointer on a scale. The spring is so designed thatits spring characteristic is straight line. The force is in the regionof 0 to 30 kg.

The mould parting forces measured with different mould parting agents,and the increase in cooling time which may be required are summarised inTable I.

Experiments Nos. 713 are comparison tests with known mould partingagents and without mould parting agent.

TABLE I wherein R is a difunctional aliphatic, cycloaliphatic, aromatic,aliphatic-aromatic or aromatic-aliphatic hydrocarbon radical or theradical R is a monofunctional aliphatic, cycloaliphatic, aromatic,

Mould parting agent N-octadecyl-isododccenyl succinic acid imideN-octadecyl-isocctadecenyl succinic acid imide.Noctadecyl-hcxahydrophthalic acid imide. N-octadccyl-tetrahydrophthalicacid imide N,N-ethylene-bis-isododecenyl succinic aci N,N-hcxamethylene-bis-isooctadecenyl succi Behenic acid Ca-steal'atc-..Stearylamine. Stcaric acid nitrile nic aci 11 Synthetic ester wax 0inomtanic acids (acid number 17,-

esterification number 145).

12 Stearyl alcohol 13 1 Measured in 1% solution in m-cresol at C.

EXAMPLE 2 10 kg. portions of polycaprolactam having a relative viscosityof 3.12 (measured in 1% solution in m-cresol at 25 C.) in the form ofgranules are homegeneously mixed by tumbling with 1 g. of finely groundtalcum and g. (0.5%) of different mould parting agents, and thenhomogenised with a conventional extruder. The polyamide is extruded as afilament of about 3 mm. diameter, chopped up into granules, and dried.

The products obtained are worked up in the manner described inExample 1. The mould parting forces required with the use of thedifferent mould parting agents and the required increase in coolingtime, if any, are summarised in Table II.

Experiments Nos. 5-9 are comparison tests with known mould partingagents.

aliphatic-aromatic or aromatic-aliphatic hydrocarbon radical or theradical R is a tetrafunctional aliphatic, cycloaliphatic, aromaticaliphatic-aromatic or aromatic-aliphatic hydrocarbon radical and R is adifunctional aliphatic, cycloaliphatic, aromatic, aliphatic-aromatic oraromatic-aliphatic hydrocarbon radical.

TABLE II Mould Increase Serial parting in cooling No. Mould partingagent force, kp. time, sec.

1 N-octadccyl-isododecenyl succinic acid imide 7. 0 0 2N-octadecylisooctadeccnylsuccinic acid imide 5. 5 0 3..N-octadecyl-hexahydrophthalimide 7. 0 0 4" N,N-ethylene-bis-isododecenylsuccinic acid imide 9. 0 0 5 Synthetic ester wax oi montanic acids (acidnumber 17, esterification 10. 0 0

number 6 Stearyl alcohol 10.5 2. 5 9. 0 0

8 l0. 0 0 9 Stcaric acid nitulc 9. 5 0

7 2. The polyamide moulding composition of claim 1 wherein theN-substituted cyclic imide is N-octadecylwherein R is a difunctionalaliphatic or cycloaliphatic hyisooctadecenyl succinic acid imide.

drocarbon radical or the radical References Cited 1? t 5 UNITED STATESPATENTS 3,309,365 3/1967 Merijan et a1. 260326.5X K FOREIGN PATENTS 31,003,083 9/1965 Great Britain.

10 and R is a difunctional aliphatic hydrocarbon radical. MORRIS LIEBMANPnmary Exammer 3. The polyamide moulding composition of claim 1 R. D.ZAITLEN, Assistant Examiner wherein said N-substituted cyclic imide isN-octadecylisododecenyl succinic acid imide. 15 C -R- 4. The polyamidemoulding composition of claim 1 326-5

